iceman

I have a TCI TH400 behind my BBC. I have had numerous problems with blowing out the moduluator valve on the tranny. I have the valve connected directly to the intake manifold port behind the carb so the valve sees full vacuum all the time. I just broke in the new cam yesterday and as soon as the motor fired the valve failed. This is the second valve in less than 2500 miles. Any ideas on what may be causing the failure?